Patients with squamous cell carcinoma of the oral cavity are afflicted with a malignancy that frequently presents with advanced disease and whose management often has profound effects upon these individual's speech, swallowing, cosmetic appearance, as well as survival. Unfortunately, despite advances in contemporary surgery and radiation therapy over the past thirty years, survival among these patients has remained essentially unaltered. Additionally, chemotherapy has shown little promise in the management of these cancers. Therefore, developing novel mechanisms of cessating the premalignant processes which lead to these malignancies may provide the most significant advancements in this field of medicine. Gene therapy for premalignancy and carcinoma in-situ of the oral cavity may be very achievable. Topical transduction of epithelium which has undergone transformation in the premalignant process is likely to be efficacious. Initial investigations of wild-type p53 adenovirus has shown promise as a molecular intervention due to its function as a tumor suppressor gene and proposed role in apoptosis. However, significant advances are required in understanding the optimization of transduction efficiency in molecular therapy as well as increasing our understanding of the interaction of molecular intervention strategies in order to produce the desired affect of tumor cell demise and sparing of non-malignant cells. We have elected to employ the adenovirus vector as a mechanism for molecular intervention due to its characteristic transient expression, efficiency of expression, and ability to expand to high titers. Additionally, lack of permanent integration is favorable from a biosafety standpoint as compared to retrovirus vectors. This proposal therefore submits to further develop our understanding of apoptosis inducing gene therapy for premalignant and microinvasive squamous cell carcinoma of the oral cavity through the following specific aims: 1. To determine the maximal transfection efficiency of adenovirus vectors in the transient expression of marker genes in organotypic and tissue slice models of premalignancies of the oral cavity. 2. To determine the effectiveness of transient expression of wild-type p53, p16, p21 (CIP/WAF1), and pRB105 independently and in combination in the induction of apoptosis in oral squamous carcinoma cell lines and the models of premalignancy. 3. To determine whether regulation of transcription factors, including p21 (CIP/WAF1), E2F-1, and DP-1, which are downstream of p53, can further potentiate the induction of apoptosis in oral squamous carcinoma cells and the models of premalignancy. 4. To determine the effect of the optimized gene therapy strategies for induction of apoptosis, in premalignant oral cavity carcinomas, upon normal oral epithelium and stromal cells.